where \([t]\)  denotes the largest integer not larger than \(t\)  and
\(\Vert \cdot \Vert \)  denotes the uniform norm on \(\mathbf {B}^d\) . The above
inequalities together with the well known Jackson inequality
[1]} imply that there exists a \(P_\rho \in \mathcal {P}_n\) 
such that for all \(f_\rho \in W_2^r\)  with \(r>\frac{d}{2}\) , there holds
\(\Vert P_\rho \Vert \le c\Vert f_\rho \Vert  \quad \mbox{and}\quad \Vert f_\rho -P_\rho \Vert ^2\le Cn^{-2r}.\) 
